The construction of ditches requires that a considerable amount of material be removed from the ground in order to provide an excavation which is at a specific elevation so that the ditch neither climbs nor descends abruptly. Construction of ditches and other excavations, such as road beds that are formed though mountains or closely adjacent to important structures often necessitates that the excavation be formed immediately adjacent to a sheer cliff, or adjacent to the vertical wall of a structure. My previous U.S. Pat. No. 4,755,001, discloses an excavating machine having a ladder type digging apparatus which includes digging apparatus attached to the sides thereof by which the width of an excavation or cut can be made wider than the throat of the excavating machine. This was achieved by the provision of opposed digging drums mounted for rotation on opposed ends of the tail shaft. The digging drums extended the width of the cut, however, the vertical dimension of the cut was equal to the diameter of the drum, and therefore unless several passes were made, the depth of the cut often was inadequate. Accordingly, a deep excavation was not practical with this digging machine without employment of additional earth moving apparatus.
The prior art U.S. Pat. No. 1,777,439 illustrates a ladder type digging boom having chain type side diggers associated therewith. The diggers are driven from the tail shaft so that a tight chain on the bottom of the side diggers was not possible with the prior art digging machine.
In the present invention, side digger chains are driven from an intermediate shaft located intermediate the head shaft and the tail shaft, thereby providing that the tight side of the side digger chain is located on the bottom of the boom, which is desirable because this location is where the digging is accomplished. Further, this arrangement enables all of the digging chains to be tensioned by sliding the boom out in the hood arrangement by which the boom is attached to the trencher main frame to thereby provide for the simultaneous tightening of all of the digging chains. Such a novel arrangement of a plurality of digging chains is not found in the prior art and provides unexpected and desirable results.